Conventionally, suspension arms which connect the vehicle body side and the wheel side through a bush are used in the vehicle suspension. As a structure of such a type of suspension arms, for example, Patent Literature 1 discloses a control arm 1 constituted by a main body 2 and a plurality of support portions 3 as illustrated in FIG. 12A. In the disclosed control arm 1, one of the plurality of support portions is a bearing journal 4 which is formed integrally with the main body 2 by bending a metal plate.
The bearing journal 4 is formed to have an approximately cylindrical shape by arranging a transition portion 5 between the main body 2 and the bearing journal 4, where the transition portion 5 extends from the main body 2 (which has an approximately U-shaped cross section) and has a funnel-like shape with the diameter gradually decreasing toward the bearing journal 4.